Add format checking for XiangShan

[Yan-Muzi]

This PR uses Scalafmt to format XiangShan source code.

Mill has built-in support for Scalafmt, which reads .scalafmt.conf to check format and reformat. Current configuration mainly includes:

• maxColumn = 120 120 characters in one line at most.
• preset = defaultWithAlign Most configurations are set to default, except that align.preset is set to more.
• Newlines section. This section is intended to work with rewrite section. Current configuration attempts to preserve line breaks in the input whenever possible.
• Rewrite section. This set of rules defines how Scalafmt rewrites some of the code. The most interesting rewrites are those related to braces. Current configuration tries to keep all the braces, except those around one line lambda expressions.
• docstring.style = keep Scalafmt does not touch existing docstrings.
• project.includePaths = ["glob:**/src/main/scala/xiangshan/**.scala"] Scalafmt only formats source files under this specific folder.

However, there is a small problem with when, elsewhen and otherwise. Scalafmt will treat them as function calls, which they are actually from the perspective of scala, instead of key words. This will lead to no space after them unlikely if or for.

Additionally, Scalafmt can be overridden or disabled in some specific regions. This allows more flexible control over how the code is formatted.

make check-format can check whether existing code is correctly formatted, and make reformat can reformat the code.

Format checking is also added to CI, but the CI will continue even if the checking fails.

[XiangShanRobot]

[Generated by IPC robot] commit: e95f196c0fd5d9b6282d30b063a2aea8d5367b95	commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
e95f196	1.808	0.447	2.043	1.187	2.938	2.508	2.291	0.921	1.369	1.441	3.454	2.658	2.399	2.932

master branch:	commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
a7828dc	1.808		2.043	1.187	2.938	2.508		0.921	1.369	1.441	3.454		2.399	2.932
9f598f8
e975de6	1.808	0.447	2.043	1.187	2.938	2.508	2.291	0.921	1.369	1.441	3.454	2.658	2.399	2.932
ff9b84b		0.447	2.043	1.187			2.291	0.921	1.369		3.454	2.658		2.932
3bec463	1.808	0.447	2.043	1.187	2.938	2.508	2.291	0.921	1.369	1.441	3.454	2.658	2.399	2.932
2d12882		0.447	2.043	1.187			2.291	0.921	1.369		3.454	2.658		2.932
ef14270	1.827	0.448	2.048	1.190	2.938	2.508	2.289	0.932	1.369	1.410	3.445	2.672	2.398	2.932
5c5f442	1.827	0.448	2.048	1.190	2.938	2.508	2.289	0.932	1.369	1.410	3.445	2.672	2.398	2.932
d67c873	1.827	0.448	2.048	1.190	2.938	2.508	2.289	0.932	1.369	1.410	3.445	2.672	2.398	2.932

[eastonman]

The current format config fits my taste well. 🥰

[XiangShanRobot]

[Generated by IPC robot] commit: b4c5b5424d56d7e1958439c61919f2eee2c92770	commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
b4c5b54	1.809	0.452	2.052	1.196	2.951	2.499	2.198	0.930	1.377	1.407	3.436	2.653	2.398	2.941

master branch:	commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
dd40a82	1.809	0.452	2.052	1.196	2.951	2.499	2.199	0.930	1.377	1.407	3.436	2.653	2.398	2.941
2a1dcaf	1.805	0.452	2.052	1.196	2.951	2.499	2.197	0.930	1.377	1.407	3.436	2.653	2.398	2.941
c08d352	1.809	0.452	2.052	1.196	2.951	2.499	2.197	0.930	1.377	1.407	3.436	2.653	2.398	2.941
87c5d21	1.805	0.452	2.052	1.196	2.951	2.499	2.199	0.930	1.377	1.407	3.436	2.653	2.398	2.941
864480f	1.809	0.452	2.052	1.196	2.951	2.499	2.199	0.930	1.377	1.407	3.436	2.653	2.398	2.941
69a3c27	1.805	0.452	2.052	1.196	2.951	2.499	2.197	0.930	1.377	1.407	3.436	2.653	2.398	2.941
a31db3f	1.805	0.452	2.052	1.196	2.951	2.499	2.197	0.930	1.377	1.407	3.436	2.653	2.398	2.941
5adc482	1.801	0.452	2.039	1.187	2.936	2.508	2.197	0.930	1.378	1.441	3.428	2.669	2.399	2.932
0d257fb	1.801	0.452	2.040	1.187	2.936	2.508	2.197	0.930	1.378	1.441	3.428	2.669	2.399	2.932
ba5ba1d	1.805	0.452	2.039	1.187	2.936	2.508	2.197	0.930	1.378	1.441	3.428	2.669	2.399	2.932